GI development

GI development US Medical PG Question 1: A 7-month-old boy is brought to the ED by his mother because of abdominal pain. Two weeks ago, she noticed he had a fever and looser stools, but both resolved after a few days. One week ago, he began to experience periodic episodes during which he would curl up into a ball, scream, and cry. The episodes lasted a few minutes, and were occasionally followed by vomiting. Between events, he was completely normal. She says the episodes have become more frequent over time, and this morning, she noticed blood in his diaper. In the ED, his vitals are within normal ranges, and his physical exam is normal. After confirming the diagnosis with an abdominal ultrasound, what is the next step in management?

• A. Supportive care
• B. Broad-spectrum antibiotics
• C. Air contrast enema (Correct Answer)
• D. Abdominal laparotomy
• E. Abdominal CT scan

GI development Explanation: ***Air contrast enema*** - An **air contrast enema** is both diagnostic and therapeutic for **intussusception**, which is strongly suggested by the patient's symptoms (colicky abdominal pain, drawing legs to chest, currant jelly stools). - It uses air pressure to **reduce the intussusception**, avoiding surgery if successful and the bowel is not compromised. *Supportive care* - While supportive care (IV fluids, pain control) is important, it does not address the underlying mechanical issue of **intussusception** and would not resolve the condition. - Delaying definitive treatment for intussusception can lead to **bowel ischemia, necrosis, and perforation**, which are life-threatening. *Broad-spectrum antibiotics* - Antibiotics are not the primary treatment for **intussusception**, as it is a mechanical obstruction, not typically a primary infection. - They might be considered if there are signs of **perforation or peritonitis**, but the immediate goal is reduction. *Abdominal laparotomy* - An **abdominal laparotomy** is a surgical intervention reserved for cases where **non-operative reduction** (like an air enema) fails or if there are signs of **bowel perforation or gangrene**. - It is not the *first-line* next step after diagnosis, especially if non-invasive options remain viable. *Abdominal CT scan* - An **abdominal CT scan** can diagnose intussusception but is typically not the preferred initial imaging because it involves **radiation exposure** and **does not offer therapeutic benefit**, unlike an air contrast enema. - Abdominal ultrasound is usually sufficient for diagnosis and safer for pediatric patients.

GI development US Medical PG Question 2: A 13-year-old girl presents to an orthopedic surgeon for evaluation of a spinal curvature that was discovered during a school screening. She has otherwise been healthy and does not take any medications. On presentation, she is found to have significant asymmetry of her back and is sent for a spine radiograph. The radiograph reveals a unilateral rib attached to the left transverse process of the C7 vertebrae. Abnormal expression of which of the following genes is most likely responsible for this finding?

• A. WNT7
• B. FGF
• C. Homeobox (Correct Answer)
• D. PAX
• E. Sonic hedgehog

GI development Explanation: ***Homeobox*** - **Homeobox genes (HOX genes)** play a crucial role in specifying the identity of vertebral segments along the **craniocaudal axis** during embryonic development. - An abnormal expression of these genes can lead to **skeletal malformations**, such as the formation of a **cervical rib**, by altering the segmental identity of the C7 vertebra. *WNT7* - **WNT7 genes** are involved in limb patterning and have a role in the formation of the **dorsoventral axis** of the limb and kidney development. - They are not primarily associated with vertebral segmentation or the formation of cervical ribs. *FGF* - **Fibroblast growth factor (FGF) genes** are essential for various processes, including limb development, neurogenesis, and angiogenesis. - While they are involved in numerous developmental pathways, they are not the primary genes responsible for specifying vertebral identity and thus cervical rib formation. *PAX* - **PAX genes** are a family of transcription factors critical for organ development, especially of the eye, brain, and kidney. - While important for development, they are not directly implicated in the specification of vertebral segments or the pathogenesis of cervical ribs. *Sonic hedgehog* - **Sonic hedgehog (SHH)** signaling is a key pathway in embryonic development, particularly for pattern formation in the neural tube, limbs, and facial structures. - While crucial for body axis development and segmentation, **HOX genes** have a more direct role in determining the specific identity of vertebral segments and causing cervical ribs.

GI development US Medical PG Question 3: A 10-month-old infant is brought in by his parents because he is vomiting and not passing stool. His parents say he has vomited multiple times over the past couple of hours, but the most recent vomit was green. The patient has no significant past medical history. On physical examination, the patient is irritable and crying. On palpation in the periumbilical region, an abdominal mass is present. Emergency laparotomy is performed, which shows a part of the patient’s intestine folded into the section adjacent to it. Which of the following is the most likely diagnosis for this patient?

• A. Pyloric stenosis
• B. Hirschsprung’s disease
• C. Duodenal atresia
• D. Intussusception (Correct Answer)
• E. Meckel’s diverticulum

GI development Explanation: ***Intussusception*** - This diagnosis is highly suggested by the classic presentation of a 10-month-old infant with **bilious vomiting**, **abdominal pain** (irritability), and an **abdominal mass** in the periumbilical region, coupled with the surgical finding of one part of the intestine telescoping into an adjacent section. - The sudden onset of symptoms in an otherwise healthy infant, along with **green vomit** (indicating bile) and an acute abdomen, are hallmark signs of this condition. *Pyloric stenosis* - This condition typically presents with **non-bilious projectile vomiting** in infants usually between 3 weeks and 6 months of age, with an **olive-shaped mass** in the epigastrium. - The patient's **bilious vomiting** and the specific finding of intestinal telescoping rule out pyloric stenosis. *Hirschsprung’s disease* - This condition usually presents with **failure to pass meconium** in the neonatal period or chronic constipation and abdominal distension in older infants. - While it involves the intestine, it is a **motility disorder** due to the absence of ganglion cells, not an anatomical telescoping of bowel. *Duodenal atresia* - This is a congenital obstruction of the duodenum, typically diagnosed shortly after birth with **bilious vomiting** and a characteristic "**double bubble**" sign on X-ray. - It would not involve an abdominal mass or the intussusception described. *Meckel’s diverticulum* - This condition is a remnant of the vitelline duct and can present with painless rectal bleeding or, less commonly, intestinal obstruction, **volvulus**, or **intussusception** if it acts as a lead point. - While it can be a rare cause of intussusception, the question directly describes the pathophysiology of intussusception itself rather than a diverticulum causing it.

GI development US Medical PG Question 4: A 4-month-old girl is brought to the physician because she has been regurgitating and vomiting 10–15 minutes after feeding for the past 3 weeks. She is breastfed and formula-fed. She was born at 38 weeks' gestation and weighed 2966 g (6 lb 9 oz). She currently weighs 5878 g (12 lb 15 oz). She appears healthy. Vital signs are within normal limits. Examination shows a soft and nontender abdomen and no organomegaly. Which of the following is the most appropriate next best step in management?

• A. Upper endoscopy
• B. Ultrasound of the abdomen
• C. Esophageal pH monitoring
• D. Positioning therapy (Correct Answer)
• E. Pantoprazole therapy

GI development Explanation: ***Positioning therapy*** - This infant is thriving, as evidenced by her significant weight gain, despite her regurgitation and vomiting. Her examination is also benign. These features make **gastroesophageal reflux (GER)**, a physiological process, the most likely diagnosis. - **Positioning therapy** (e.g., keeping the infant upright during and after feeds) is a first-line, conservative management strategy for GER in infants who are otherwise healthy and gaining weight well. *Upper endoscopy* - **Upper endoscopy** is an invasive procedure and is typically reserved for evaluating patients with suspected complicated gastroesophageal reflux disease (GERD), such as those with **poor weight gain**, **hematemesis**, or **esophagitis**, none of which are seen here. - It would not be the initial step in a thriving infant with symptoms consistent with uncomplicated GER. *Ultrasound of the abdomen* - An **abdominal ultrasound** is primarily used to diagnose **pyloric stenosis** in infants, which typically presents with **projectile, non-bilious vomiting** and **poor weight gain** or weight loss, usually between 3 and 6 weeks of age. - This infant's symptoms are different in character (regurgitation/vomiting 10-15 minutes after feeding, not projectile) and she is gaining weight well, making pyloric stenosis less likely. *Esophageal pH monitoring* - **Esophageal pH monitoring** is used to quantify acid reflux episodes and is typically reserved for infants with atypical symptoms, suspected **complicated GERD**, or those who have failed empirical therapy. - It is not indicated as a primary diagnostic or management step in a healthy, thriving infant with typical GER symptoms. *Pantoprazole therapy* - **Proton pump inhibitors (PPIs)** like pantoprazole are used to treat **GERD** by reducing stomach acid production, especially in cases with evidence of **esophagitis** or significant symptoms impacting growth or comfort. - Given this infant is thriving and has no signs of complications, acid-suppressing medication is not appropriate as the initial management step; conservative measures should be tried first.

GI development US Medical PG Question 5: A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?

• A. "Does the diarrhea typically precede the constipation, or vice-versa?"
• B. "Is the diarrhea foul-smelling?"
• C. "Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life"
• D. "Are the symptoms worse in the morning or at night?"
• E. "Can you tell me more about the symptoms you have been experiencing?" (Correct Answer)

GI development Explanation: ***Can you tell me more about the symptoms you have been experiencing?*** - This **open-ended question** encourages the patient to provide a **comprehensive narrative** of their symptoms, including details about onset, frequency, duration, alleviating/aggravating factors, and associated symptoms, which is crucial for diagnosis. - In a patient presenting with vague, intermittent symptoms like alternating constipation and diarrhea, allowing them to elaborate freely can reveal important clues that might not be captured by more targeted questions. *Does the diarrhea typically precede the constipation, or vice-versa?* - While knowing the sequence of symptoms can be helpful in understanding the **pattern of bowel dysfunction**, it is a very specific question that might overlook other important aspects of the patient's experience. - It prematurely narrows the focus without first obtaining a broad understanding of the patient's overall symptomatic picture. *Is the diarrhea foul-smelling?* - Foul-smelling diarrhea can indicate **malabsorption** or **bacterial overgrowth**, which are important to consider in some gastrointestinal conditions. - However, this is a **specific symptom inquiry** that should follow a more general exploration of the patient's symptoms, as it may not be relevant if other crucial details are missed. *Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life* - Quantifying pain intensity is useful for assessing the **severity of discomfort** and monitoring changes over time. - However, for a patient with intermittent rather than acute, severe pain, understanding the **character, location, and triggers** of the pain is often more diagnostically valuable than just a numerical rating initially. *Are the symptoms worse in the morning or at night?* - Diurnal variation can be relevant in certain conditions, such as inflammatory bowel diseases where nocturnal symptoms might be more concerning, or functional disorders whose symptoms might be stress-related. - This is another **specific question** that should come after gathering a more complete initial picture of the patient's symptoms to ensure no key information is overlooked.

GI development US Medical PG Question 6: A 23-year-old man comes to the physician for evaluation of decreased hearing, dizziness, and ringing in his right ear for the past 6 months. Physical examination shows multiple soft, yellow plaques and papules on his arms, chest, and back. There is sensorineural hearing loss and weakness of facial muscles bilaterally. His gait is unsteady. An MRI of the brain shows a 3-cm mass near the right internal auditory meatus and a 2-cm mass at the left cerebellopontine angle. The abnormal cells in these masses are most likely derived from which of the following embryological structures?

• A. Surface ectoderm
• B. Neural tube
• C. Neural crest (Correct Answer)
• D. Notochord
• E. Mesoderm

GI development Explanation: ***Neural crest*** - The patient's symptoms (bilateral sensorineural hearing loss, facial weakness, unsteady gait, central masses) along with cutaneous lesions (soft, yellow plaques) are highly suggestive of **Neurofibromatosis type 2 (NF2)**. - NF2 is characterized by **vestibular schwannomas** (acoustic neuromas) and other CNS tumors, which are derived from **Schwann cells**. Schwann cells, along with melanocytes and other peripheral nervous system components, originate from the **neural crest**. *Surface ectoderm* - The surface ectoderm forms structures such as the **epidermis**, hair, nails, and anterior pituitary. - While the skin lesions are present, the primary tumors (schwannomas) are not derived from the surface ectoderm. *Neural tube* - The neural tube gives rise to the **central nervous system** (brain and spinal cord) and motor neurons. - While the tumors affect the brain and cranial nerves, the specific cell type forming schwannomas (Schwann cells) does not originate directly from the neural tube. *Notochord* - The notochord induces the formation of the neural tube and eventually degenerates, contributing to the **nucleus pulposus** of the intervertebral discs. - It is not involved in the pathogenesis or cellular origin of schwannomas. *Mesoderm* - The mesoderm gives rise to connective tissues, blood, bone, muscle, and most internal organs. - While some tumors can have mesodermal origins, schwannomas are neuroectodermal in origin.

GI development US Medical PG Question 7: An 11-year-old girl is brought to the office by her mother due to complaint of intermittent and severe periumbilical pain for 1 day. She does not have any significant past medical history. She provides a history of a recent school trip to the suburbs. On physical examination, there is a mild tenderness around the umbilicus without any distension or discharge. There is no rebound tenderness. Bowel sounds are normal. An abdominal imaging shows enlarged mesenteric lymph nodes, and she is diagnosed with mesenteric lymphadenitis. However, incidentally, a mass of tissue was seen joining the inferior pole of both kidneys as shown in the image. Which of the following best describes this renal anomaly?

• A. Fused kidneys ascend beyond superior mesenteric artery.
• B. Rapid progression to acute renal failure
• C. Kidneys are usually non-functional.
• D. Increased risk of developing renal vein thrombosis
• E. Association with ureteropelvic junction obstruction (UPJO) (Correct Answer)

GI development Explanation: ***Association with ureteropelvic junction obstruction (UPJO)*** - **Horseshoe kidney** is characterized by the fusion of the lower poles (most common) or upper poles of the kidneys, forming a U-shape. This anomaly is associated with an increased incidence of **ureteropelvic junction obstruction (UPJO)** due to the abnormal course of the ureters over the isthmus. - The abnormal ascent of the fused kidneys can also lead to an increased incidence of other anomalies such as **vesicoureteral reflux**, **renal calculi**, and recurrent urinary tract infections. *Fused kidneys ascend beyond superior mesenteric artery.* - The **horseshoe kidney** typically **fails to ascend** completely during development because its isthmus (the fused part) can get trapped under the **inferior mesenteric artery**. - Therefore, fused kidneys in horseshoe kidney are often found in a **lower position** than normal, not ascended beyond the superior mesenteric artery. *Rapid progression to acute renal failure* - While horseshoe kidney can be associated with an increased risk of complications (like UPJO, stones, infections), it does not inherently lead to **rapid progression to acute renal failure**. - Many individuals with a horseshoe kidney have **normal renal function** without significant clinical manifestations. *Kidneys are usually non-functional.* - The presence of a horseshoe kidney **does not typically mean the kidneys are non-functional**. - In most cases, both renal units of a horseshoe kidney are **functional**, although they may be at increased risk for complications that could impact function over time. *Increased risk of developing renal vein thrombosis* - There is **no established increased risk** of developing **renal vein thrombosis** specifically associated with horseshoe kidney. - The primary vascular anomalies associated with horseshoe kidney relate to the arterial supply and variations in the number and origin of renal arteries, not typically venous thrombosis.

GI development US Medical PG Question 8: An investigator is studying the effects of an antihypertensive drug during pregnancy. Follow-up studies show that the drug can adversely affect differentiation of the ureteric bud into its direct derivatives in fetuses exposed during the first trimester. Which of the following structures is most likely to develop incorrectly in the affected fetus?

• A. Collecting ducts (Correct Answer)
• B. Proximal convoluted tubule
• C. Loop of Henle
• D. Bladder
• E. Distal convoluted tubule

GI development Explanation: ***Collecting ducts*** - The **ureteric bud** is an outgrowth of the **mesonephric (Wolffian) duct** that directly gives rise to the **collecting ducts**, minor and major calyces, renal pelvis, and ureter. - An adverse effect on the differentiation of the ureteric bud during the first trimester would directly impact the development of these structures, potentially leading to renal dysplasia or collecting system abnormalities. - **Clinical correlation**: ACE inhibitors and ARBs are contraindicated in pregnancy due to their teratogenic effects on fetal renal development. *Proximal convoluted tubule* - The **proximal convoluted tubule** develops from the **metanephric mesenchyme**, not from the ureteric bud. - This structure is part of the nephron proper, which forms when the metanephric mesenchyme is induced by the ureteric bud to differentiate. *Loop of Henle* - The **loop of Henle** also develops from the **metanephric mesenchyme**. - While its formation depends on inductive signals from the ureteric bud, it is not a direct derivative of the ureteric bud itself. *Bladder* - The **bladder** develops from the **urogenital sinus**, which is derived from the ventral part of the **cloaca** after partitioning by the urorectal septum. - Its development is distinct from the derivatives of the ureteric bud, though they are functionally connected. *Distal convoluted tubule* - The **distal convoluted tubule** develops from the **metanephric mesenchyme**. - It is a component of the nephron and connects to the collecting duct but is not a direct derivative of the ureteric bud.

GI development US Medical PG Question 9: A 45-year-old woman comes to the physician because of progressive difficulty swallowing solids and liquids over the past 4 months. She has lost 4 kg (9 lb) during this period. There is no history of serious illness. She emigrated to the US from Panama 7 years ago. She does not smoke cigarettes or drink alcohol. Cardiopulmonary examination shows a systolic murmur and an S3 gallop. A barium radiograph of the chest is shown. Histopathologic examination of the esophageal wall is most likely to show which of the following?

• A. Presence of intranuclear basophilic inclusions
• B. Atrophy of esophageal smooth muscle cells
• C. Infiltration of eosinophils in the epithelium
• D. Presence of metaplastic columnar epithelium
• E. Absence of myenteric plexus neurons (Correct Answer)

GI development Explanation: ***Absence of myenteric plexus neurons*** - This finding is pathognomonic for **Chagas disease** (American trypanosomiasis), caused by *Trypanosoma cruzi*, endemic to Central and South America including Panama. - The parasite destroys the **myenteric (Auerbach's) plexus neurons** in the esophageal wall, disrupting normal peristalsis and leading to **megaesophagus**. - This results in **progressive dysphagia for both solids and liquids** and weight loss, as seen in this patient. - The **cardiac findings** (systolic murmur and S3 gallop) indicate associated **chagasic cardiomyopathy**, another manifestation of chronic Chagas disease. *Presence of intranuclear basophilic inclusions* - Suggestive of **cytomegalovirus (CMV) esophagitis**, typically seen in immunocompromised patients (HIV/AIDS, transplant recipients). - This patient has no immunocompromised state, and CMV does not cause the cardiac manifestations or chronic megaesophagus seen here. *Atrophy of esophageal smooth muscle cells* - Not characteristic of Chagas disease or achalasia; these conditions typically show **smooth muscle hypertrophy** due to chronic obstruction. - Muscle atrophy would not explain the dysphagia, megaesophagus, or cardiac findings. *Infiltration of eosinophils in the epithelium* - Indicates **eosinophilic esophagitis**, an allergic condition usually presenting with food impaction and dysphagia mainly for solids. - Would not explain the cardiac manifestations or the epidemiological connection to Panama. *Presence of metaplastic columnar epithelium* - Represents **Barrett's esophagus**, a complication of chronic gastroesophageal reflux disease (GERD). - The patient's presentation with dysphagia for both solids and liquids, cardiac disease, and megaesophagus on barium study points to a **motility disorder** (Chagas disease), not reflux disease.

GI development US Medical PG Question 10: A 4-week-old boy is brought to the emergency department with a 2-day history of projectile vomiting after feeding. His parents state that he is their firstborn child and that he was born healthy. He developed normally for several weeks but started to eat less 1 week ago. Physical exam reveals a small, round mass in the right upper quadrant of the abdomen close to the midline. The infant throws up in the emergency department, and the vomitus is observed to be watery with no traces of bile. Which of the following is associated with the most likely cause of this patient's symptoms?

• A. Chloride transport defect
• B. Recanalization defect
• C. Vascular accident
• D. Failure of neural crest migration
• E. Nitric oxide synthase deficiency (Correct Answer)

GI development Explanation: ***Nitric oxide synthase deficiency*** - This symptom constellation points to **pyloric stenosis**, which is characterized by smooth muscle hypertrophy and concurrent deficiency of **nitric oxide synthase** and possibly **interstitial cells of Cajal** in the pylorus. - The thickened pylorus creates an obstruction, leading to non-bilious projectile vomiting, an "olive-like" mass, and subsequent electrolyte imbalances. *Chloride transport defect* - A chloride transport defect, particularly in the **CFTR (cystic fibrosis transmembrane conductance regulator) gene**, is characteristic of cystic fibrosis. - While cystic fibrosis can cause gastrointestinal symptoms like **meconium ileus** or malabsorption, it does not typically present with projectile vomiting and a palpable abdominal mass in this age group, nor is it the primary cause of pyloric stenosis. *Recanalization defect* - **Recanalization defects** refer to issues in the development of a lumen in structures that are initially solid during embryogenesis, such as the gut tube. - This can lead to conditions like **duodenal atresia**, which typically presents with **bilious vomiting** (due to obstruction distal to the ampulla of Vater) and often a "double-bubble" sign on imaging, which is not described here. *Vascular accident* - A **vascular accident** in the gut can lead to conditions such as **necrotizing enterocolitis** in neonates or **bowel ischemia/infarction**. - These conditions would typically present with symptoms like bloody stools, abdominal distension, lethargy, and systemic signs of illness, rather than isolated projectile vomiting and an abdominal mass. *Failure of neural crest migration* - **Failure of neural crest cell migration** is the underlying cause of **Hirschsprung disease**, where there is an absence of ganglion cells in the distal colon. - This typically presents with **constipation**, abdominal distension, and failure to pass meconium, rather than projectile vomiting, and usually affects the large intestine.

GI development Flashcard 1 of 10

Question: Which embryological structure develops into the liver and gallbladder? _____

Answer: Foregut

Extra Information:  Watch associated Bootcamp video [https://app.bootcamp.com/med-school/gastroenterology/videos/visceral-anatomy?index=2] https://onlinemeded.org?ref=anki 

GI development Flashcard 2 of 10

Question: What is the most common congenital anomaly of the GI tract? _____

Answer: Meckel diverticulum

GI development Flashcard 3 of 10

Question: Malrotation is a congenital anomaly of _____ rotation during fetal development

Answer: midgut

Extra Information:   Watch Congenital GI Disorders [https://dashboard.sketchy.com/study/medical/courses/medical-pathophysiology/units/medical-pathophysiology-gi/videos/medical-pathophysiology-gi-small-bowel-disorders-congenital-gi-disorders?utm_source=anki&utm_medium=partnership&utm_campaign=february_update&utm_content=medical]Watch associated Bootcamp video [https://app.bootcamp.com/med-school/gastroenterology/videos/intestinal-pathology?index=9] https://onlinemeded.org?ref=anki 

GI development Flashcard 4 of 10

Question: Which congenital abdominal wall defect IS covered by peritoneum?_____

Answer: Omphalocele

GI development Flashcard 5 of 10

Question: Which embryological structure develops into the GI tract from the distal duodenum to the proximal 2/3 of the transverse colon? _____

Answer: Midgut

GI development Flashcard 6 of 10

Question: Which embryological structure develops into the GI tract from the lower esophagus to the proximal duodenum? _____

Answer: Foregut

GI development Flashcard 7 of 10

Question: Meckel's diverticulum

Answer: failure of vitelline duct to close

Extra Information: in newborn: melena, periumbilical pain, ulcer

GI development Flashcard 8 of 10

Question: gut tube epithelium

Answer: endoderm

GI development Flashcard 9 of 10

Question: liver

Answer: endoderm

GI development Flashcard 10 of 10

Question: gallbladder

Answer: endoderm